Automobiles particularly ones of small size, in order to achieve optimal high gas milage must and do utilize small alternators and low capacity battery. A difficulty with such small alternator and battery is that there is insufficient electrical power to quickly heat the automobile with the electrical heater. Accordingly there is no apparent way heretofore to utilize a supplemental electrical heater either with or without an auxilliary battery since such small alternator often would prove to cause excessively low voltage when recharging the auxilliary battery.
Typically, for requisite quick heating of automobile space, an electrical heater of 3600 watts is needed if the auto passenger space is to be heated within about two to four minutes, for example. For a full-sized low gas-efficient automobile, the alternator or generator is normally about 100 amperes; when accelerating from an original 1500 RPM to about 4500 RPM, the large alternator or generator will increase from typically (100.times.12) 1200 watts energy to 3600 watts energy. This is sufficient power to quickly heat a car passenger space by use of such a 3600 watt electrical heater. On the other hand, alternator amperage for gas-efficient small cars is about 35 amperes; acceleration from about 1500 RPM to 3,000 RPM will double the amperes from 35 to 70 amperes, which for a 12 volt battery increases wattage from 420 watts to 840 watts, far short of the 3600 watts needed for a 3600 watt electrical heater. Even if the acceleration were tripled from 1500 to 4500 RPM (revolutions per minute), the resulting wattage would be a mere 1260 watts, hardly one-third of needed energy for a 3600 watt electrical heater. An electrical heater of lower wattage would be insufficient to accomplish the needed result of heating automobile passenger space within typically three minutes or less.
It should be noted, as general information, that voltage of batteries for large and small automobiles is substantially the same, ranging typically from about 10.5 volts to about 13 volts.